Communication device, communication method, integrated circuit, and electronic instrument

This technology pertains to a communication device, a communication method, an integrated circuit, and an electronic instrument that make it possible to reduce the manufacturing costs of a communication device comprising both RF tag and reader/writer functions, or an electronic instrument into which this communication device is installed. When a transmission circuit operates in a first operation mode as an RFID reader/writer, transmission data is transmitted to a communication destination using a first carrier generated by an antenna unit, by performing load modulation that changes the impedance of the antenna unit in accordance with the transmission data; and when the transmission circuit operates in a second operation mode as a communication destination of an RFID reader/writer, the transmission data is transmitted to the RFID reader/writer using a second carrier received by the antenna unit, by performing load modulation that changes the impedance of the antenna unit in accordance with the transmission data. This technology can be applied, for example, to either a communication device comprising both RF tag and reader/writer functions, or an electronic instrument into which this communication device is installed.